1. Field of the Invention
The present invention relates to a molding method of a mold product having a thin film at an inner surface thereof including a primary molding step of molding a half mold product by a sliding die and a fixed die, and a film forming step of forming a thin film on one face of the half mold product provided by the step and a molding apparatus used for carrying out the molding method, further specifically, relates to a molding method of a mold product having a thin film at an inner surface thereof including a primary molding step of molding a pair of half mold products to provide bonding portions by a sliding die and a fixed die, a film forming step for forming a thin film at a surface of one of the half mold products provided by the primary molding step, and a secondary molding step of matching the one half mold product molded with the thin film by the film forming step with other half mold product of the pair of mold products and fastening the dies to bond at the bonding portions and a molding apparatus used in carrying out the molding method.
2. Description of the Related Art
As a hollow mold product having a thin film of an order of several μm at a portion of an inner surface of a hollow member, for example, a front lamp, a tail lamp or the like mounted to a vehicle can be pointed out. The lamp includes a main body portion in a recess shape attached with a bulb and a lens portion integrally attached to an opening portion of the main body portion. The main body portion is molded by, for example, injection molding, further, hung down by using an exclusive hanger at inside of a vacuum tank exclusive for film forming by masking an unnecessary portion of an outer surface or the like, successively, formed with the thin film by a film forming method mentioned later. Further, the main body portion formed with the thin film and the lens portion molded separately from the main body portion are set to respective dies and integrated by matching/butting together edges of an opening portion of the main body portion and the lens portion and injecting a molten resin to bonding portions butted together to thereby mold a hollow mold product having the thin film at an inner surface thereof.
There has been proposed a film forming method of forming the thin film at the inner surface of the main body portion or a surface of a board. For example, a sputtering method of forming the thin film by making the board intended to form the thin film and a target opposed to each other, applying a negative voltage of several kV to the target in an argon gas atmosphere of about several Pa through several tens Pa and discharging electricity, a vacuum film forming method of forming the film by containing the board and an evaporation source at inside of a vacuum vessel, an ion plating method of forming the film in vacuum under a pressure of argon gas of several Pa by applying a negative voltage of several kV to a board, a chemical film forming method, and the like has been proposed.
JP-B-2-38377 discloses a molding method of the hollow mold product by injection molding. The molding method includes primary molding of molding a pair of half hollow mold products each to provide a bonding portion at a surrounding of an opening portion thereof by a pair of cavities configured by fixed dies and sliding dies, a step of opening the dies such that one of the half mold products remains on a side of the fixed die and other of the half hollow mold products remains on a side of the sliding die, further, sliding the sliding die to a position where the bonding portions of the pair of half hollow mold products match, successively passing, fastening the dies, and secondary molding of injecting a molten resin to the bonding portions to bond thereafter.
Japanese Patent No. 3677033 discloses a molding method of a hollow mold product having a thin film at an inner surface thereof including primary molding of a pair of half mold products by the injection molding method disclosed in JP-B-2-38377, and secondary molding of opening the dies thereafter such that one of the half hollow mold products remains at the sliding die and other half hollow mold product remains on a side of the fixed die, sliding the sliding die such that the half mold product remaining at the sliding die is opposedly brought into close contact with a recess portion for film forming provided at the fixed die, forming the thin film at the inner surface of the half hollow mold product by a film forming chamber provided at the recess portion for film forming, thereafter, sliding the sliding die to a position where bonding portions of the pair of half mold products match, successively, sliding the dies, and injecting the molten resin to the bonding portions to bond together.
According to the method disclosed in Japanese Patent No. 3677033, a step of temporarily detaching the primary mold product to carry to the vacuum tank for film forming is not needed. Therefore, a failure in film forming by contaminating a film forming face brought about by adhering dirt from the hand, dust or the like to the primary mold product can be prevented in carrying the primary mold product. Further, respective steps of injection molding of the pair of half hollow mold products, forming the thin film by film forming, thereafter, bonding the pair of half hollow mold products by secondary injection molding and providing a finished product of the hollow mold product having the thin film at the inner surface can be automated.
However, in Japanese Patent No. 3677033, the film forming chamber for carrying out film forming is provided at inside of the fixed die for carrying out the primary injection molding, and therefore, a number of problems are posed. For example, the die for injection molding and the film forming chamber for film forming are provided at inside of the same die. Thus, the film forming chamber may be influenced by a temperature by injection molding to bring about a strain. Further, the film forming chamber is strained also by a stress by a die fastening force for injection molding. As a result, a hermetically closing performance for achieving vacuum necessary for film forming may be difficult to be ensured. In this way, since a vacuum degree necessary for film forming is difficult to be ensured, it may be difficult to form a film on other mold product simultaneously while carrying out injection molding. This fact poses a problem in a molding method of molding two or more of hollow mold products each having a thin film at an inner surface thereof efficiently in parallel constituting one aspect of the invention described later. Further, an adjustment of a position of the die for pertinently carrying out injection molding and an adjustment of a position of the film forming chamber for pertinently carrying out film forming cannot be carried out independently from each other since the film forming chamber is provided at inside of the fixed die. This fact also poses a problem in view of maintenance that a degree of freedom of the adjustments is low. Further, since the film forming chamber is integrated to the fixed die for injection molding, a total of the mold is enlarged. Thus, it becomes difficult to fabricate the dies, and cost for fabricating the dies becomes high.